This invention relates to fluid powered systems and in particular to fluid powered linkages and engines.
In many hydraulic or pneumatic systems, a master cylinder or pump is fluidly connected to a slave cylinder to transmit force or work to a remote location. When master and slave cylinders of unequal diameters are used, the force applied by the slave cylinder may be more or less than the force applied to the master cylinder. Similarly, the displacement of the slave cylinder may be more or less than the displacement of the master cylinder. In these systems, however, there is always a linear relationship between the force or displacement of the slave cylinder and the force or displacement of the master cylinder. Similarly, when a pump is used to drive a slave cylinder, the force exerted by the slave cylinder is always linearly related to the pressure produced by the pump. To achieve any other relationship requires additional mechanical linkages at one end. Similarly, the design of hydraulic or pneumatic engines using cylindrical linkages is limited by such linear relationships.
An object of the present invention is to provide a fluid powered, preferably hydraulic, linkage with non-linear relationships between (a) the flow, volume or pressure of fluid added to the linkage and (b) the displacement of the linkage or the force applied by the linkage. Another object is to provide an apparatus for producing a fluid output with altered pressure, volume or flow compared to a fluid input. Yet another object of the present invention is to provide an engine using a linkage as mentioned above. These objects are met by the combination of features, steps or both found in the independent claims, the dependent claims disclosing further advantageous embodiments of the invention. The following summary may not describe all necessary features of the invention which may reside in a sub-combination of the following features or in a combination with features described in other parts of this document.
In one aspect, the invention provides a fluid powered linkage having at least three sides of substantially equal width joined by connectors to form a polygon of variable cross sectional area. Side plates enclose a variable volume within the polygon. At least one port allows fluid to enter into or leave from the enclosed variable volume in a controllable manner. Seals prevent fluid from entering or leaving the enclosed variable volume other than through the one or more ports. Two abutments are located on the sides or connectors and the distance between the two abutments varies non-linearly with, but in the same direction as, the variable cross-sectional area. Optionally, an inner surface of one or more of the sides defines a recess.
Preferred linkages have a cross-section in the shape of a diamond or rhombus of varying internal angles, or a half or quarter thereof. Where the cross-section is a diamond, four sides are connected by hinges. The four sides are of about equal length and the abutments are located substantially at the obtuse angles of the diamond. In use, the obtuse angle preferably ranges from nearly 180 degrees to about 135 degrees. A preferred seal is made of a resilient membrane forming a plenum which varies in volume as the membrane expands or contracts. The membrane is placed with the variable volume enclosed by the linkage and a port connects the interior of the plenum with the outside of the linkage.
In another aspect, the invention relates to an apparatus for producing a fluid output with altered pressure, volume or flow compared to a fluid input. The apparatus comprises a linkage as described above and a piston movable in a cylinder to vary an enclosed volume in the cylinder. A cylinder port allows fluid to exit or enter the enclosed volume of the cylinder. A rod between one of the two abutments of the linkage and the piston ties the movement of one to the other. One or more spacing members to hold the other of the two abutments of the linkage at a constant spacing from the cylinder. Preferably, the area of the piston is equal to or slightly more than the area of each of a side of a diamond-shaped linkage and less than twice the area of a side of the diamond-shaped linkage.
In yet another aspect, the invention relates to a fluid powered motor comprising the apparatus described above.